linux-kernel - [PATCH v5 1/2] module: add module_elf_check

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Date:   Mon, 31 Oct 2022 22:07:32 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     linux-modules@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:     Nicholas Piggin <npiggin@...il.com>, linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Jessica Yu <jeyu@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH v5 1/2] module: add module_elf_check_arch for module-specific checks

The elf_check_arch() function is also used to test compatibility of
usermode binaries. Kernel modules may have more specific requirements,
for example powerpc would like to test for ABI version compatibility.

Add a weak module_elf_check_arch() that defaults to true, and call it
from elf_validity_check().

Cc: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Jessica Yu <jeyu@...nel.org>
[np: added changelog, adjust name, rebase]
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
 include/linux/moduleloader.h |  3 +++
 kernel/module/main.c         | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 9e09d11ffe5b..7b4587a19189 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -13,6 +13,9 @@
  * must be implemented by each architecture.
  */
 
+/* arch may override to do additional checking of ELF header architecture */
+bool module_elf_check_arch(Elf_Ehdr *hdr);
+
 /* Adjust arch-specific sections.  Return 0 on success.  */
 int module_frob_arch_sections(Elf_Ehdr *hdr,
 			      Elf_Shdr *sechdrs,
diff --git a/kernel/module/main.c b/kernel/module/main.c
index d02d39c7174e..7b3f6fb0d428 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1674,6 +1674,11 @@ static int elf_validity_check(struct load_info *info)
 		       info->hdr->e_machine);
 		goto no_exec;
 	}
+	if (!module_elf_check_arch(info->hdr)) {
+		pr_err("Invalid module architecture in ELF header: %u\n",
+		       info->hdr->e_machine);
+		goto no_exec;
+	}
 	if (info->hdr->e_shentsize != sizeof(Elf_Shdr)) {
 		pr_err("Invalid ELF section header size\n");
 		goto no_exec;
@@ -2247,6 +2252,11 @@ static void flush_module_icache(const struct module *mod)
 			   (unsigned long)mod->core_layout.base + mod->core_layout.size);
 }
 
+bool __weak module_elf_check_arch(Elf_Ehdr *hdr)
+{
+	return true;
+}
+
 int __weak module_frob_arch_sections(Elf_Ehdr *hdr,
 				     Elf_Shdr *sechdrs,
 				     char *secstrings,
-- 
2.37.2